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strlcpy.S revision 1.5 
      1 /*	$NetBSD: strlcpy.S,v 1.5 2020/05/05 06:20:55 skrll Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2002 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Matthew Fredette.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <machine/asm.h>
     33 
     34 #if defined(LIBC_SCCS) && !defined(lint)
     35         RCSID("$NetBSD: strlcpy.S,v 1.5 2020/05/05 06:20:55 skrll Exp $")
     36 #endif /* LIBC_SCCS and not lint */
     37 
     38 /*
     39  * size_t strlcpy(char *dst, const char *src, size_t size);
     40  */
     41 LEAF_ENTRY(_strlcpy)
     42 	.weak strlcpy
     43 	strlcpy = _strlcpy
     44 
     45 	/* Always load the first byte of the source string. */
     46 	ldbs,ma		1(%arg1), %r1
     47 
     48 	/*
     49 	 * If our dst buffer is zero bytes, branch immediately
     50 	 * to the code that counts the (remaining) length
     51 	 * of the src string.
     52 	 */
     53 	comb,=		%r0, %arg2, $strlcpy_dst_done
     54 	 copy		%arg1, %ret0
     55 
     56 	/*
     57 	 * If our dst buffer is one byte, branch immediately
     58 	 * to the code that NUL-terminates the dst buffer and
     59 	 * counts the (remaining) length of the src string.
     60 	 */
     61 	addib,=,n	-1, %arg2, $strlcpy_dst_full
     62 
     63 	/*
     64 	 * Loop copying bytes.  At the top of this loop,
     65 	 * %arg2 is always the number of bytes we can still
     66 	 * store, and %r1 holds the next byte to store.
     67 	 */
     68 $strlcpy_loop:
     69 	comb,=		%r0, %r1, $strlcpy_exit
     70 	 stbs,ma	%r1, 1(%arg0)
     71 	addib,<>	-1, %arg2, $strlcpy_loop
     72 	 ldbs,ma	1(%arg1), %r1
     73 
     74 $strlcpy_dst_full:
     75 	stbs,ma		%r0, 1(%arg0)
     76 
     77 $strlcpy_dst_done:
     78 	comb,<>,n	%r0, %r1, $strlcpy_dst_done
     79 	ldbs,ma		1(%arg1), %r1
     80 
     81 $strlcpy_exit:
     82 	bv		%r0(%rp)
     83 	 sub		%arg1, %ret0, %ret0
     84 EXIT(strlcpy)
     85